Electrons- Electrons were discovered by Professor James Chadwick. He had discovered that electrons are negatively charged sub-atomic particles which can move from one atom to another to form compounds.
- Electrons also have very low mass compared to its neighbor sub-atomic particles.
- Electrons revolve around the nucleus in different orbits, and every orbit has a different size and number of electrons depending on its energy.
- Number of electrons increase from one energy level to another as the size of orbits increase in ascending order.
Protons and Nucleus- Protons were discovered by Rudherford who concluded that protons were positively charged sub-atomic particles which were present inside a central spherical ball like shape called nucleus.The nucleus has the highest mass compared to the sub-atomic particles.
- Electrons are attracted by the force of the nucleus which is known as a electromagnetic force.
-The Nucleus has positive charge ( due to Protons) whereas electrons are negatively charged particles.Opposites charge attracts in this case and hence this structure forms the atom of an element.
Neutrons-Neutrons were the last sub-atomic particles discovered by Goldstein. They were heavy particles which are present in the nucleus as well.
- Neutrons have different rate of mass compared to protons and electrons, and are neutrally charged.
- To find the number of neutrons present in a nucleus we subtract the atomic mass number by the atomic number of an atom.
- The atomic number is equal to the number of electrons and protons in an atom. Bohr's Model of the Atom
The Structure of an Atom
Drawbacks of Bohr's Model
Goes against Heisenberg's Principal of uncertainity
Cannot explain the fine spectra of elements
Quantum Mechanic Model
The most recent model of the atom. It's based on the theory that the energy levels within an atom are further divided into subshell (s,p,d,f) and that eletrons fill up these subshells before moving on to the successive energy level. This model also supports Heisenberg's principle because according to this model there's only a high probablility of finding electron within the energy levels. The exact location of the electron are difficult to pinpoint.
Orbitals
The three dimensional space around the nucleus within an atom where there is a high probablity of locating electrons. They are also known as subshells and they are labelled s,p,d and f and they are placed in the order of increasing energy.
Quantum Numbers
These are four numbers that are used to locate electrons within an atom. According to Pauli's Exclusion Principle, no two electrons in an atom have all 4 of the same quantum numbers. The quantum numbers are the following:
Principal Quantum Number 'n': It specifies the location and energy of an electron, it is a measure of the effective volume or size of the electron cloud denoted by ‘n’ and can have values 1,2,3,4....
Angular Momentum Quantum Number 'l':
It determines the shape of the orbital. It takes integral values from 0 to (n-1) where 'n' is the principal quantum number. Whn 'l' = 1 it means the p-orbital of an energy level.
Magnetic Moment Quantum Number 'm':
It gives the orientation of the orbitals in space. When m= -1...0...1 it signifies the p-orbital which has 3 orientations and that it can hold 6 eletrons.
Spin Quantum Number 's':
It indicates the direction in which the electron rotates on its own axis. It's represented by the letter 's' and s= +1/2 or -1/2.
Chapter 2 -
Compounds- A Compound is a fusion of two or more elements. Metals combined with non-metals form ionic compounds and non-metals combined with other non-metals form molecular compunds.
Ionic Bonds: Ionic bonds are formed when a metal loses its electron(s) to a non-metal and they both become oppositely charged.Sodium and Chlorine together form an ionic bond when they react and the resulting compound is known as Sodium Chloride. Sodium and Chlorine are very harmful elements in their elemental state however safe when they form into a compound. The common name for Sodium Chloride is salt which is added in food.
- Symbol of Sodium is Na and Chlorine is Cl and they form (NaCl), which is a compound.
- Sodium is a positively charged element since it gives an electron whereas Chlorine is a negatively charged element since it accepts an electron.
- During this bond Sodium looses one electron from its outermost shell and gives it to Chlorine to complete its outer shell. Transfer of electron happens in order to form a stable compound ( NaCl).
Sodium and Chlorine forming an ionic bond.
Covalent bonds :
Covalent bonds are formed when two non-metals react with each and share the electrons in their outer shell to acheive a full outer shell. For example hydrogen and chlorine form a covalent bond [H - Cl] which results in the molecular compound hydrochloric acid.
Shapes of molecules:
Molecules
'VESPR' Shape
Bond Angle
Example
HX
Linear
-
H - Cl, H - F
AX₂
Linear
180º
CO₂
AX₃
Trigonal
120º
BF₃
AX₃E
Pyramidal
107º
:NH₃
AX₂E₂
V-shape or Bent
104.5º
H₂:O:
AX₄
Tetrahedral
109.5º
CH₄
AX₅
Trigonal bipyramidal
120º and 90º
PCL₅
AX₆
Octahedral
90º
SF₆
Polar Covalent Bonds: If a covalent bond is formed between two atoms with a significant difference in electronegativety (greater than 0.7) they are considered to have formed a polar covalent. Chapter 3
Chapter 1- The Nature of Matter
Sub-atomic particles in an atom
Electrons- Electrons were discovered by Professor James Chadwick. He had discovered that electrons are negatively charged sub-atomic particles which can move from one atom to another to form compounds.
- Electrons also have very low mass compared to its neighbor sub-atomic particles.
- Electrons revolve around the nucleus in different orbits, and every orbit has a different size and number of electrons depending on its energy.- Number of electrons increase from one energy level to another as the size of orbits increase in ascending order.
Protons and Nucleus- Protons were discovered by Rudherford who concluded that protons were positively charged sub-atomic particles which were present inside a central spherical ball like shape called nucleus.The nucleus has the highest mass compared to the sub-atomic particles.
- Electrons are attracted by the force of the nucleus which is known as a electromagnetic force.
-The Nucleus has positive charge ( due to Protons) whereas electrons are negatively charged particles.Opposites charge attracts in this case and hence this structure forms the atom of an element.
Neutrons- Neutrons were the last sub-atomic particles discovered by Goldstein. They were heavy particles which are present in the nucleus as well.
- Neutrons have different rate of mass compared to protons and electrons, and are neutrally charged.
- To find the number of neutrons present in a nucleus we subtract the atomic mass number by the atomic number of an atom.
- The atomic number is equal to the number of electrons and protons in an atom. Bohr's Model of the Atom
Drawbacks of Bohr's Model
Quantum Mechanic Model
The most recent model of the atom. It's based on the theory that the energy levels within an atom are further divided into subshell (s,p,d,f) and that eletrons fill up these subshells before moving on to the successive energy level. This model also supports Heisenberg's principle because according to this model there's only a high probablility of finding electron within the energy levels. The exact location of the electron are difficult to pinpoint.
Orbitals
The three dimensional space around the nucleus within an atom where there is a high probablity of locating electrons. They are also known as subshells and they are labelled s,p,d and f and they are placed in the order of increasing energy.
Quantum Numbers
These are four numbers that are used to locate electrons within an atom. According to Pauli's Exclusion Principle, no two electrons in an atom have all 4 of the same quantum numbers. The quantum numbers are the following:
Principal Quantum Number 'n' :
It specifies the location and energy of an electron, it is a measure of the effective volume or size of the electron cloud denoted by ‘n’ and can have values 1,2,3,4....
Angular Momentum Quantum Number 'l' :
It determines the shape of the orbital. It takes integral values from 0 to (n-1) where 'n' is the principal quantum number. Whn 'l' = 1 it means the p-orbital of an energy level.
Magnetic Moment Quantum Number 'm' :
It gives the orientation of the orbitals in space. When m= -1...0...1 it signifies the p-orbital which has 3 orientations and that it can hold 6 eletrons.
Spin Quantum Number 's' :
It indicates the direction in which the electron rotates on its own axis. It's represented by the letter 's' and s= +1/2 or -1/2.
Chapter 2 -
Compounds- A Compound is a fusion of two or more elements. Metals combined with non-metals form ionic compounds and non-metals combined with other non-metals form molecular compunds.
Ionic Bonds: Ionic bonds are formed when a metal loses its electron(s) to a non-metal and they both become oppositely charged.Sodium and Chlorine together form an ionic bond when they react and the resulting compound is known as Sodium Chloride. Sodium and Chlorine are very harmful elements in their elemental state however safe when they form into a compound. The common name for Sodium Chloride is salt which is added in food.
- Symbol of Sodium is Na and Chlorine is Cl and they form (NaCl), which is a compound.
- Sodium is a positively charged element since it gives an electron whereas Chlorine is a negatively charged element since it accepts an electron.
- During this bond Sodium looses one electron from its outermost shell and gives it to Chlorine to complete its outer shell. Transfer of electron happens in order to form a stable compound ( NaCl).
Sodium and Chlorine forming an ionic bond.
Covalent bonds :
Covalent bonds are formed when two non-metals react with each and share the electrons in their outer shell to acheive a full outer shell. For example hydrogen and chlorine form a covalent bond [H - Cl] which results in the molecular compound hydrochloric acid.
Shapes of molecules:
Polar Covalent Bonds:
If a covalent bond is formed between two atoms with a significant difference in electronegativety (greater than 0.7) they are considered to have formed a polar covalent.
Chapter 3